Steel cased .45 ACP ammo was intended for use in the M3 "Grease Guns" but was also approved for the Thompsons. It wasn't approved for use in 1911 pistols, though some of it surely found its way into the guns. It largely came about as an expedient response to shortages of brass that was needed for higher pressure rifle ammunition and such...about the same time that the government started issuing steel pennies to conserve copper.

Although it can be reloaded, it's not really meant to be, and due to the lack of springback after pressure levels dropped...tended to be a little hard on pistol extractors. It also gets brittle and splits on about the 3rd loading. Yeah. Ask me how I'd know about that.

All that I've seen was headstamped '41-'43. Yours...loaded in the 50s...is the most recent that I've ever heard tell of. I suppose some of the drawn cases were still in the pipeline following WW2, and not stamped. Interesting.

TW is the only headstamp I've seen, but I'm pretty sure that Evans Chrysler (EC) also contracted for some of it in 1944. No production figures on any of it, but the majority was produced by Twin Cities Arsenal. I've heard of some that came from Saint Louis, but have never seen any documentation.

Correction. Fingers in gear while brain in neutral. TWA wasn't connected to Twin Cities Arsenal.
Gotta slow down and stop watchin' TV while I surf the boards.